1. Field of the Invention
The present invention relates generally to optical switches and transparent electrodes for an optical switch, and more particularly, to the use of magnetron cathodes for high current pulsed plasma discharges in large aperture plasma electrode Pockels cells.
2. Description of Related Art
System architectures for very large inertial confinement fusion (ICF) lasers require active optical elements with apertures on the order of one meter. Large aperture optical switches are needed for isolation of stages, switch-out from regenerative amplifier cavities and protection from target retro-reflections. In operation, it is necessary to apply a voltage uniformly to the crystal faces. No conventional optical switch technology is scalable to such large apertures. Pockels cells conventionally utilize coaxial ring electrodes but Pockels cells with ring electrodes require crystal thickness comparable to the aperture. Thin crystal Pockels cell designs using transparent conducting metallic films or liquid layers have also been proposed, but have unacceptable resistivity at large apertures or are not appropriate for use with high intensity laser beams. Other potential approaches include fast Faraday rotators or transient volumetric thermal gratings.
A thin crystal can be used to construct a longitudinal Pockels cell if one has transparent electrodes which apply a uniform electric field along the crystal optical axis coincident with the propagation direction of the laser beam. Thin crystals are also required for efficient second harmonic generation with ICF lasers, and a longitudinal configuration with transparent electrodes can be utilized for an electro-optically tuned second harmonic switch. See U.S. Pat. No. 4,615,588 which states that the plasma can be created either by a main high voltage pulser used to charge up the crystal or by auxiliary discharges or external sources of ionization, however, the only voltage pulsers discussed are a thyratron with a pulse charged cable and a self triggered, low inductance spark-gap. See U.S. Pat. No. 5,045,166 for a method and apparatus for producing a high density ionic gas discharge in a magnetron.